Process for the preparation of higher fatty acid monoglycerides



United States Patent 3,083,216 PRQCESS FGR THE PRElARATlQN @F H Gl lEl-l FATTY ACID MQNGGLYCERKDES William Godfrey Alsop, Summit, NJ, and frying .loseph Krems, Vienna, Austria, assignors to olgate-Palmelive Company, New York, N.Y., a corporation of Delaware N0 Drawing. Filed Apr. 6, 1950, Ser. No. 20,252 7 Claims. (Cl. 260410.7)

The present invention relates to a process for the preparation of a monoester of glycerine with a higher fatty acid containing from 16 to 18 carbon atoms.

It has previously been proposed to prepare higher fatty acid monoglyceride esters by reacting glycerine with C1648 higher fatty acids or with glyceryl polyesters such as glyceryl diesters of triesters of such higher fatty acids.

The prior art suggests the use of excess glycerine in amounts of from to about 15 moles per mole of fatty acylating agent in carrying out this process in order to favor the formation of monoglyceride esters in perference to diglyceride esters. Nevertheless, in the case of acylations involving higher fatty acids of 16 to 18 carbon atoms, the product obtained according to the prior art process is usually characterized by a glyceryl monoester content of a maximum of about 60% or less, a diester content on the order of about 35%, and a triester content of about 5%.

The present process enables the preparation of glyceryl monoesters of higher fatty acids containing from 16 to 18 carbon atoms by direct reaction between glycerine and an acylating agent such as a higher fatty acid, fatty acid diglyceride, or fatty acid triglyceride, to produce a fatty acid monoglyceride of high purity, i.e. containing at least 85% rnoncester and not more than about 15% of diester.

In accordance with the present invention, a process for the preparation of a higher fatty acid monoglyceride comprises commingling and reacting an acylating agent containing a fatty acid radical having from about 16 to 18 carbon atoms with glycerine at a temperature of at least about 270 C. to form higher fatty acid monoglyceride, said glycerine being employed in excess of the stoichiometric amount required to form glyceryl monoester of said fatty acid radical, said higher fatty acid monoglyceride dissolving completely Within said excess glycerinc to form a solution therein, cooling said glycerine solution of monoglyceride to a temperature below about 100 C. within about 3 minutes to form two liquid phases, one of said phases containing principally higher fatty acid monogiyceride and glycerine and the other liquid phase consisting essentially of glycerine, separating said liquid phases, and recovering substantially pure hi her fatty acid monoglyceride from said liquid phase containing higher fatty acid monoglyceride in admixture with glycerine.

In carrying out the present process it is essential to the preparation of a high purity product as hereinabove defined that the glycerine, which is employed as both a reactant and a solvent, be employed in an amount which dissolves all of the monoglyceride product formed by reaction between the glycerine and the acylating agent at the reaction temperature employed. Thus, in comparison with prior art processes wherein first the acylating agent and then the monoglyceride product are used as solvents for the glycerine, the process of the present invention uses extraordinarily high ratios of glycerine to acylating agent, eg in the case of fatty triglycerides, typical proportions of reactants will be on the order of 1000 parts by weight of glycerine per part by weight of triglyceride. This corresponds to a mole ratio of total glycerine present in the system to fatty acyl groups on 3,083,216 Patented Mar. 26, 1953 the order of about 3200:l, and in the case of fatty diglycerides and fatty acids, the same molecular proportion may be employed. While it is preferred to operate at approximately this 3200:1 mole ratio, higher ratios may be employed of course, but substantially lower ratios will result in poorer yields of the desired pure monoglyceride because of the limited solubility of the fatty material in the glycerine and the need for the formation of a clear homogeneous single phase solution in order to assure formation of substantially pure monoglyceride. It is unnecessary to use ratios substantially greater than about 3200zl, in addition to which such higher ratios tend to increase problems of recovery of the pure monoglyceride and separation thereof from the unreacted glycerine.

Operating temperature used in carrying out the instant process characteristically are on the order of about 270 to 295 C. and above. At temperatures substantially below about 270 C. the solubility of fatty acid monoglycerides in glycerine diminishes markedly. On the other hand, at temperatures above about 295 C., which is approximately the boiling point of glycerine at one atmosphere, pressurized equipment is required.

The present process is normally performed in the absence of atmospheric oxygen, which may conveniently be excluded by carrying out the operation under an inert atmosphere such as nitrogen, carbon dioxide or hydrogen, using a slight positive pressure to prevent entry of air into the system. A non-acid neutral or alkaline catalyst may also be employed, suitable such catalysts being inter alia, water, caustic soda, lime, alkali metal alcoholates such as sodium ethoxylate, and the like. Typically these catalysts are employed in an amount ranging from about 0.000l% to 0.001% by weight of the reactants.

In carrying out the present process, the fatty acylating agent is dissolved in glycerine at an elevated temperature as hereinbefore indicated. The glycerine and the acylating agent may be heated together or the glycerine may be preheated and the acylating agent added thereto. Heating is done, of course, under an inert or oxygen-free atmosphere, and the mixture of reactants is agitated in order to facilitate reaction of the acylating agent and the formation of a true solution of the monoglyceride product in the glycerine in a reasonably short time. Catalyst may be supplied by being added separately or in admixture with either of the two reactants.

lfter the ractants have been commingled at the desired reaction temperature, reaction normally occurs substantially immediately to bring about the formation of a single phase system constituting a solution of fatty acid monoglyceride in glycerine. Suitably however, the reaction mixture may be agitated at 270 C. or higher for a period of about 1 to 10 minutes or longer to insure complete reaction, after which the solution obtained is rapidly cooled to a temperature not greater than about C. Rapid cooling is employed in order to prevent reversion of the monoglyceride to higher esters during the formation of a separate, glycerine-poor liquid phase which occurs on cooling of the heated single phase solution. (Although the rate of reversion of the monoglyceride ester to an equilibrium mixture of mono-, diand tri-esters is rapid at temperatures above about 155 C., it is substantially diminished by about C. At temperatures of about 100 C. and below the rate of reversion is extremely slow and the monoglyceride may, for practical purposes, be considered stable at such low temperatures.) Thus it has been found desirable to cool the solution within a period not appreciably greater than about 3 minutes.

in the present process, rapid cooling of the heated monoglyceride reaction product to a temperature below 100 C. brings about formation of a two-phase system which readily separates into a lower or glycerine layer and an upper liquid layer which contains substantially purehigher fatty acid monoglyceride emulsified with, and containing dissolved therein, excess glycerine. These layers are easily separated by decantation or centrifuging and the fatty acid monoglyceride in the upper layer may thereafter be recovered by separation from the glycerine therein by various methods including washing with aqueous solutions of inorganic salts such as 5% sodium sulphate, vacuum distillation, or vacuum-steam distilla tion. If desired, any alkaline catalyst present in the fatty acid monoglyceride may be deactivated by neutraliz ation with phosphoric acid or with acid phosphates such as sodium diacid phosphate.

Fatty acylating agents employed in carrying out the present process include fatty acids, fatty acid diesters of glycerine and fatty acid triesters of glycerine in which acylating agents the fatty acid component contains from 16 to 18 carbon atoms. Examples of such acylating agents are'palrnitic, stearic and oleic acids per se, glyceryl distearate, glyceryl dipalmitate, glyceryl dioleate, and triesters including naturally occurring as well as modified fats such as tallow, corn oil, soy bean oil, cotton seed oil, and their hydrogenated products, and mixtures thereof.

The process of the present invention is specifically applicable to the preparation of mono-fatty acid esters of glycerine wherein the fatty acid contains 16 to 18 carbon atoms. This is so because in the case of the preparation of monoesters of lower fatty acids in accordance with previously proposed procedures, glycerine is sufiiciently soluble in the monoglycerides thereof to permit the realization of reasonably high purity monoglycerides using a 5 to 15 mole excess of a glycerine. A similar consideration of increased solubility applies in the case of the preparation of esters of propylene glycol, and it appears that the monoesters of glycerine with higher fatty acid esters of at least 16 carbon atoms are unique in their low solvent power for glycerine.

The following examples are given to additionally illustrate the nature of the invention and it will be understood that the invention is not limited thereto. Thus, althought batch processes are illustrated, the present process may be conveniently carried out on a continuous basis, utilizing concurrent flow of glycerine, acylating agent, and catalyst through a heated contacting column. All parts and proportions in the following examples are by weight unless specifically indicated to be otherwise.

Example I One part of glyceryl monostearate which contains about 50% of glyceryl monostearate, 35% glyceryl distearate, 5% of glyceryl tristearate, and free glycerine is mixed with 1000 parts of glycerine heated to about 280 C. The mixed esters dissolve almost instantly to form a clear solution. The solution is agitated at 280 C. under a nitrogen atmosphere, and the glyceryl polyesters react with the glycerine in which they are dissolved to form a single phase, clear glycerine solu tion of glyceryl monostearate, a reaction which occurs substantially immediately upon mixing. Agitation and heating of the solution is continued for about 4 minutes, after which the solution is cooled to 100 C. within a period of about 2 minutes. The cooled product contains two distinct liquid phases, which are separated by centrifuging, and the lighter phase which consists of glyceryl monostearate with glycerine dissolved therein and emulsified therewith is subjected to vacuum distillation at 1 mm. of mercury and l00-140 C. to remove the glycerine therefrom. 'Ihis distilled glycerine is recombined with the previously separated lower glycerine phase for reuse in the reaction.

The glycerine-free glyceryl monostearate product so obtained contains about 90% glyceryl monostearate and only about 10% glyceryl distearate.

In this reaction, moisture dissolved in the glycerine employed as the reactant acts as'a catalyst, sulilcient moisture for this purpose being retained in the glycerine even at the reaction temperature employed.

Example II One part of fallow is mixed with 1000 parts of glycerine which has been heated to 280 C. under a nitrogen atmosphere. 0.001 part of caustic soda is added to act as a catalyst. The tallow, which dissolves almost immediately in the glycerine, reacts to form a clear, single phase solution of tallow fatty acid monoglyceride in glycerine, which after heatingat 280 C. for about 10 minutes, is cooled to C. in 3 minutes. On cooling, a system of two liquid phases is formed. The system is centrifuged and the phases separated. The lighter phase, which comprises monoglyceride having glycerine emulsified and dissolved therein, is subjected to vacuum distillation at 140 C. and 1 mm. of mercury and the glycerine is removed. On removal of glycerine from the lighter layer, the product which is obtained contains 90% glyceryl monoester of tallow fatty acids and 10% of the glyceryl diester of tallow fatty acids.

Although the present invention has been described with reference to particular embodiments and examples, it will be apparent to those skilled in the art that variations and modifications of this invention can be made and that equivalents can be substituted thereto without departing from the principles and true spirit of the invention.

What is claimed is:

1. A process for the preparation of a higher fatty acid monoglyceride which comprises commingling an acylating agent containing a fatty acid radical having from about 16 to 18 carbon atoms with glycerine at a temperature of at least about 270 C., said glycerine being present in excess of the amount required both to form stoichiometrically the glyceryl monoester of the said fatty acid radical and to dissolve completely said stoichiometric amount of said glyceryl monoester, and reacting said acylating agent and said glycerine to form a solution of higher fatty acid monoglyceride in glycerine cooling said glycerine solution of monoglyceride to a temperature below about C. within about 3 minutes to form two liquid phases, one of said phases containing principally higher fatty acid monoglyceride and glycerine and the other liquid phase consisting essentially of glycerine, separating said liquid phases, and recovering sub stantially pure higher fatty acid monoglyceride from said liquid phase containing higher fatty acid monoglyceride in admixture with glycerine.

2. A process for the preparation of a higher fatty acid monoglyceride as set forth in claim 1 wherein said acylating agent is a fatty triglyceride.

3. A process for the preparation of a higher fatty acid monoglyccride as set forth in claim 1 wherein said acylating agent is a fatty diglyceride.

4. A process for the preparation of higher fatty acid monoglyceride as set forth in claim 1 wherein said glycerine is commingled with said acylating agent and the resulting mixture is maintained at at least about 270 C for a period up to about 10 minutes.

5. A process for the preparation of a higher fatty acid monoglyceride which comprises commingling and reacting an acylating agent containing a fatty acid radical 1 having from about 16 to 18 carbon atoms with glycerine at a temperature of at least about 270 C., the mole ratio of fatty acyl groups in said acylating agent to total glyceryl present being about 123200, to form a solution of fatty acid monoglyceride in glycerine, cooling said glycerine solution of monoglyceride to a temperature below about 100 C. within about 3 minutes to form two liquid phases,.one of said phases containing principally higher fatty acid monoglyceride and glycerine and the other liquid phase consisting essentially'of glycerine, separating said liquid phases, and recovering substantially pure higher fatty acid monoglyceride from said liquid phase containing higher fatty acid monoglyceride in admixture with glycerine.

6. A process for the preparation of a higher fatty acid monoglyceride which comprises commingling an acylating agent containing a fatty acid radical having from 16 to 18 carbon atoms with glycerine at a temperature from! about 270 to 295 C., said glycerine being present in excess of the amount required both to form stoichiometrically the glyceryl monoester of the said fatty acid radical and to dissolve completely said stoichiometric amount of said glyceryl monoester, and reacting said acylating agentand said glycerine to form a solution of higher fatty acid monoglyceride in glycerine, cooling said glycerine solution of said monoglyceride to a temperature below about 100 C. within about 3 minutes to form two liquid phases, one of said phases containing principally said higher fatty acid monoglyceride and glycerine and the other liquid phase consisting essentially of glycerine, separating said liquid phases, and removing said glycerine from said monoglyceride-containing phase to produce substantially pure higher fatty acid monoglyceride.

7. A process for the preparation of a higher fatty acid monoglyceride which comprises commingling a triglyc; eride with a higher fatty acid having from about 16 to 18 carbon atoms with glycerine at a temperature from about 270 to 295 C. under an inert atmosphere, said glycerine being present in excess of the amount required both to form stoichiometrically the glyceryl monoester of said fatty acid and to dissolve completely said stoichiometric amount of said glyceryl monoester, and reacting said fatty acid and said glycerine to form a clear, single phase solution of higher fatty acid monoglyceride in glycerine, cooling said solution of said monoglyceride in glycerine to a temperature below about C. within about 3 minutes to form a lighter liquid phase and a heavier liquid phase, said lighter liquid phase containing principally higher fatty acid monoglyceride and dissolved and emulsified glycerine and said heavier liquid phase consisting essentially of glycerine, separating said liquid phases, and vacuum distilling said dissolved and emulsified glycerine out of said lighter liquid phase to produce a residue of substantially pure higher fatty acid monoglyceride.

References Cited in the file of this patent UNITED STATES PATENTS Kuhrt Apr. 7, 1953 2,732,387 Brokaw et al. Jan. 24, 1956 2,744,124 Alsop May 1, 1956 OTHER REFERENCES Bailey: Industrial Oil and Fat Products, 2nd Ed., Interscience Publishers, Inc., New York, 1951, pp. 819 to 826. 

1. A PROCESS FOR THE PREPARATION OF A HIGHER FATTY ACID MONOGLYCERIDE WHICH COMPRISES COMMINGLING AN ACYLATING AGENT CONTAINING A FATTY ACID RADICAL HAVING FROM ABOUT 16 TO 18 CARBON ATOMS WITH GLYCERINE AT A TEMPERATURE OF AT LEAST ABOUT 270*C., SAID GLYCERINE BEING PRESENT IN EXCESS OF THE AMOUNT REQUIRED BOTH TO FORM STOICHIOMETRICALLY THE GLYCERYL MONOESTER OF THE SAID FATTY ACID RADICAL AND TO DISSOLVE COMPLETELY SAID STOICHIOMETRIC AMOUNT OF SAID GLYCERYL MONOESTER, AND REACTING SAID ACYLATING AGENT AND SAID GLYCERINE TO FORM A SOLUTION OF HIGHER FATTY ACID MONOGLYCERIDE IN GLYCERINE COOLING SAID GLYCERINE SOLUTION OF MONOGYLCERIDE TO A TEMPERATURE BELOW ABOUT 100*C. WITHIN ABOUT 3 MINUTES TO FORM TWO LIQUID PHASES, ONE OF SAID PHASES CONTAINING PRINCIPALLY HIGHER FATTY ACID MONOGLYCERIDE AND GLYCERINE AND THE OTHER LIQUID PHASE CONSISTING ESSENTIALLY OF GLYCERINE, SEPARATING SAID LIQUID PHASES, AND RECOVERING SUBSTANTIALLY PURE HIGHER FATTY ACID MONOGLYCERIDE FROM SAID LIQUID PHASE CONTAINING HIGHER FATTY ACID MONOGLYCERIDE IN ADMIXTURE WITH GLYCERINE. 